1) A series of experiments have been performed to investigate the biological effects of murine interleukin-6 (IL-6). Initial studies have demonstrated that this factor may be involved in both B- and T-cell development. IL-6 enhances proliferation of thymocytes treated with lectin and IL-1. A similar enhancement is observed with IL-4, and combinations of these factors have begun to define a hierarchy of action for three well-characterized cytokines. The role of IL-6 in B-cell development has been examined in the immune response to influenze hemmagglutinin. Antisera to IL-6 completely inhibit the primary response to this antigen and the inhibition is reversed by the addition of purified IL-6. In contrast, the antisera has no effect on the secondary response indicating an obligatory requirement for this factor in the early stages of the B-cell response and a differential responsiveness of primary versus secondary cells. 2) Studies have been initiated to identify genes and proteins associated with cell differentiation. Clonal cell lines which can be induced to differentiate are being used to construct subtractive cDNA libraries for gene isolation. Nuclear matrix preparations are simultaneously being analyzed to determine the magnitude of expressed protein differences between successive developmental - stages and to potentially isolate specific proteins.